Morrison Hershfield’s work on the Toronto-York Spadina Subway Extension Twin Tunnels project – as part of an integrated project team working on construction management – was named the Canadian Project of the Year by the Tunnelling Association of Canada.

The Tunnelling Association of Canada (TAC) annually presents the Canadian Project of the Year Award to a team that has significantly contributed to a project in Canada that demonstrates the highest level of engineering skill, insight and understanding of underground construction.

From TTC.ca’s write-up of the award:

TBM (tunnel boring machine) tunnelling progressed with minimal settlements and excellent ring build quality being achieved. The project overcame a number of challenges associated with the alignment which passes near or directly beneath many existing buildings, as well as sensitive buried and surface utilities. Detailed assessment of the settlement effects of tunnelling on these buildings was performed which identified a key concern with tunnelling beneath the York University’s Schulich Building. Tunnelling beneath the Schulich Building was completed with maximum achieved movement of less than 3mm.

Also, a triple-track section required for the turnback of trains was located beneath an existing power transmission corridor and major gas pipelines. Following a detailed analysis of options, the Sequential Excavation Method (SEM) was selected as a superior alternative which involved a multi-stage excavation and lining sequence – the first large scale implementation of this tunnelling methodology in the Toronto area. This was also the first major use of SEM in soft-ground in Canada.

Other project innovations included the introduction of guide rods on the segment radial joints that significantly improved ring build quality and tunnelling productivity, and the first use of steel-fibre reinforced concrete (SFRC) lining rings (100 ring test section) on a transit tunnel in Canada.

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